I am a little confused as to the documentation and the implications of :build_embedded option and the priv directory.

I know that build_embedded: false creates a symlink to my project priv directory. For my dependencies, symlinks are also created for their private directories.So, in the end I have symlinks form _lbuild/... to my priv and to priv directories under deps.
With build_embedded: true all this symlinks become copies.

Since Elixir 1.5 we do not have the line build_embedded: Mix.env() == :prod in the mix.exs template anymore. With the reasoning we don’t need this line anymore.
And from here on I am confused. Why don’t we need the line anymore? When I build a release I have symlinks that can’t be resolved anymore. I cannot find any reference to this behavior in the documentation. Therefore I think I have misunderstood something. There is an Elixir issue and another post that don’t help me either.